{
TASK:minjumps
LANG:PASCAL
}
program minjumps;
var i,a,b,n,p,f,z:longint;
    skok:longint;
begin
 read(a,b,n);
 if a<b then
 begin
 p:=a;
 a:=b;
 b:=p;
 end;

 if (n mod 2 <>0)and(a mod 2 =0 )and (b mod 2=0) then
  begin
  writeln('-1');
  exit;
  end;
 if (b>a)and(n mod b=0)then
  begin
   writeln(n div b);
   exit;
  end;
 if (a>b)and(n mod a=0 )then
  begin
   writeln(n div a);
   exit;
  end;

 for i:=1 to 100 do
  begin
   z:=1;
   f:=0;
   while n>((i*a)+(z*b)) do
     inc(z);
   if n=((i*a)+(z*b)) then
    begin
     skok:=(i+z);
     writeln(skok);
     exit;
    end;
   if z>1 then
   inc(f);
   while (n<((i*a)-(z*b)))and(f=0)  do
    inc(z);
   if n=((i*a)-(z*b)) then
    begin
     skok:=(i+z);
     writeln(skok);
     exit;
    end;
  end;

end.